BASENAME, DIRNAME - reference manual online

Parse pathname components.

Chapter

2015-08-08

BASENAME(3) Linux Programmer's Manual BASENAME(3)NAME
basename, dirname - parse pathname components
SYNOPSIS
#include <libgen.h>
char *dirname(char *path);
char *basename(char *path);
DESCRIPTION
Warning: there are two different functions basename() - see below.
The functions dirname() and basename() break a null-terminated pathname string into direc‐
tory and filename components. In the usual case, dirname() returns the string up to, but
not including, the final '/', and basename() returns the component following the final
'/'. Trailing '/' characters are not counted as part of the pathname.
If path does not contain a slash, dirname() returns the string "." while basename()
returns a copy of path. If path is the string "/", then both dirname() and basename()
return the string "/". If path is a null pointer or points to an empty string, then both
dirname() and basename() return the string ".".
Concatenating the string returned by dirname(), a "/", and the string returned by base‐
name() yields a complete pathname.
Both dirname() and basename() may modify the contents of path, so it may be desirable to
pass a copy when calling one of these functions.
These functions may return pointers to statically allocated memory which may be overwrit‐
ten by subsequent calls. Alternatively, they may return a pointer to some part of path,
so that the string referred to by path should not be modified or freed until the pointer
returned by the function is no longer required.
The following list of examples (taken from SUSv2) shows the strings returned by dirname()
and basename() for different paths:
path dirname basename
/usr/lib /usr lib
/usr/ / usr
usr . usr
/ / /
. . .
.. . ..
RETURN VALUE
Both dirname() and basename() return pointers to null-terminated strings. (Do not pass
these pointers to free(3).)
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌──────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────┼───────────────┼─────────┤
│basename(), dirname() │ Thread safety │ MT-Safe │
└──────────────────────┴───────────────┴─────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
There are two different versions of basename() - the POSIX version described above, and
the GNU version, which one gets after
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <string.h>
The GNU version never modifies its argument, and returns the empty string when path has a
trailing slash, and in particular also when it is "/". There is no GNU version of
dirname().
With glibc, one gets the POSIX version of basename() when <libgen.h> is included, and the
GNU version otherwise.
BUGS
In the glibc implementation of the POSIX versions of these functions they modify their
argument, and segfault when called with a static string like "/usr/". Before glibc 2.2.1,
the glibc version of dirname() did not correctly handle pathnames with trailing '/' char‐
acters, and generated a segfault if given a NULL argument.
EXAMPLE
char *dirc, *basec, *bname, *dname;
char *path = "/etc/passwd";
dirc = strdup(path);
basec = strdup(path);
dname = dirname(dirc);
bname = basename(basec);
printf("dirname=%s, basename=%s\n", dname, bname);
SEE ALSObasename(1), dirname(1)COLOPHON
This page is part of release 4.04 of the Linux man-pages project. A description of the
project, information about reporting bugs, and the latest version of this page, can be
found at http://www.kernel.org/doc/man-pages/.GNU 2015-08-08 BASENAME(3)